Time delay undervoltage protective system



5- D. F. RICHARDSON 2,010,701

TIME DELAY UNDERVOLTAGE PROTECTIVE SYSTEM Filed Jan. 10, 1955 h'wvencor: Dudleg F. Richardson,

Att orne 9 Patented Aug. 6, 1935 UNITED STATES TIME DELAY UNDERVOLTAGE PROTECTIVE SYSTEM Dudley F. Richardson, Chappaqua, N. Y., assignor to General Electric Company, a corporation of N ew York Application January 10, 1935, Seral No.

Claims. (Cl. 175-294) My invention relates to a control system which affords time delay protection in the event of a dip in the line voltage, more particularly to a time relay undervoltage protective system which 5 provides for the instantaneous deenergization of a load circuit in response to the eration of a push button, and has for an object the provision of a simple, reliable and inexpensive system of this character.

Heretofore no-voltage protective de ices have been provided in systems so that translating devices are deenergized in the event that the line voltage decreases a predetermined amount or suddenly drops to zero. It has furthermore been proposed to provide a time delay opening of the no-voltage protective device by means of various forms of mechanical, hydraulic or electrical timing devices. In every case the timing device has been connected to complete the holding circuit of the load contactor. In many cases in order to deenergize the load controlling contactor it has been necessary to hold a stop push button in the open circuit position for a time interval greater than that provided by the timing device.

In carrying out my invention in one form, I provide a control circuit which by means of a momentary opbutton can accomplish the deenergization of the load contactor without holding the stop push button in the closed circuit position more than an instant. More specifically, I provide a relay with normally closed contacts connected in the contactor holding circuit.

For a more complete understanding of my invention, reference should now be had to the accompanying drawing wherein I have shown diagrammatically in Fig. l a system embodying one form of my invention, Fig. 2 illustrating diagrammatically a modification of my invention. Referring to the drawing, I have shown my invention in one form as applied to a motor it! provided with a field winding H. The motor H3 is arranged to be connected to the supply lines I2 and [3 by means of a contactor M provided with interlock l6. g closed circuit position it is necessary only to depress momentarily a normally open start push tactor operating coil it, normally closed contacts 22 of an overload device 23, and by conductor 24 to the other supply line it. The interlock contacts i5 operable by the closing of the contactor l4 thereupon complete an energizing circuit for an operating coil 25 of an undervoltage protective device 25. The device 26 operates without a time delay to close its contacts 2?. However, by any suitable means, for example a dashpot 28, the operation of the device 26 to its open circuit position is delayed for a predetermined time interval. Incident to the clos of the contacts 2? a holding circuit is completed for the contactor operating coil it, which circuit may be traced from the supply line i 2 by the contacts 27, contacts 2! of the control relay 2!, contactor operating coil 16, overload contacts 22, and by conductor 24 to the other supply line i3.

In case of a predetermined reduction in the line voltage the load controlling contactor l4 immediately operates to an open circuit position to deenergize the timing device and the motor It If the voltage of the supply lines i2 and i 3 should increase above this predetermined value before the device 26 operates to open its contacts 21', the contactor M will reclose and the energizing circuit for the coil 25 of the timing device will again be completed. In this manner motor, H3 is only temporarily disconnected from the supply lines !2 and L3 in case of momentary dips in the voltage of the supply lines.

In case it is necessary to deenergize instantly the motor l0, it is necessary only to depress momentarily a normally open stop push button 29 to complete a circuit for an operating coil 30 provided for the control relay 2!. This circuit may be traced from the supply line i by the contacts of stop push button 23, operating coil 30, and by conductor 3. to the other supply line 13. The relay contacts 20 thereupon interrupt the holding circuit for the contactor coil it which contractor opens and deencrgizes the motor H). At the same time the contacts 32 of the relay iii are operated to a closed circuit position to complete a maintaining circuit for the relay operating winding This circuit may be traced from the supply line l2, by contacts 21 of the undervoltage device conductor contacts 32 of the control relay 2!, the operating coil 3! and by conductor 35 to the other supply line i 3. The control relay 2! is therefore held in the energized position to maintain its contacts 20 in the open circuit position. As soon, however, as the tmclervoltage device operates to the open circuit position b th the maintaining circuit for the relay coil 39 and the holding circuit for the contactor operating coil 56 are interrupted.

If the control relay 2! were not provided it would be necessary to connect a normally closed cover any such stop push button in circuit with either the contactor operating coil it or the operating coil 25 of the undervoltage device. With such an arrangement when the contactor it is to be deengized the stop push button must be held in an open circuit position at least until the timing device 26 opens its contacts. By means of my invention, however, the motor it or other load can be either energized or deenergized by the momentary operation of the start or stop push buttons.

In the modification of my invention shown in Fig. 2, the start and stop push buttons El and 29 of the momentary contact type are connected in identically the same manner with respect to the control relay 2i as in Fig. l. a separate undervoltage protective device, however, as shown in Fig. 2 a load controlling contactor 33 is provided with a one way driving connection 3% arranged to operate aicontact 35 to the closed circuit position as the contactor closes the load circuit to the motor it. The contact 35 'operates with a time delay to the open circuit position by reason of the provision of a timing means such, for example, as the dashpot 36. The contact '35 performs the same circuit controlling functions as the contacts Zl of Fig. 1.

While I have shown particular embodiments of my invention, it will be understood, of course, that I do not wish to be limited thereto since many modifications may be made, and I, therefore, contemplate by the. appended claims to modifications as fall within the true spirit and scope of my invention. a

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A time delay undervoltage protective system comprisinga cont actor for controlling the energization of a load circuit, a time delay undervoltage deviceresponsive to a predetermined voltage or" said load circuit for maintaining a holding circuit for said contactor, normally closed contacts connected in said holding circuit,'an operating coil for said contacts, means for momentarily energizing said operating coil to open said normally closed contacts and thereby open said holding circuit, and auxiliary switching means operated by said coil for completing a maintaining circuit for said coil including said undervoltage device whereby said coil maintains said normally closed contacts in open circuit position until said undervoltage device opens said holding circuit. 7

2. A time delay undervoltage protective system comprising a contactor for controlling the energization of a load circuit, a start push button for momentarily energizing said contactor to operate it to a closed position, time delay means operable by the closing or" said contactor for completing a holding circuit to maintain said contactor in said closed position, said time delay means being operable with a time delay from a closed circuit position to an open circuit position upon a predetermined reduction in the voltage of said load circuit, a relay provided with normally closed contacts connected in series circuit relation with said holding circuit, a stop push button for momentarily energizing said relay to open said holding circuit, and means operable with said relay for completing a maintaining circuit for said relay, said maintaining circuit including said time delay means whereby said rerelay provided with mally open and closed contacts, said normally Instead of utilizingvided with an operating lay is deenergized after said time delay means operates to its open circuit position.

3. A time delayundervoltage protective system comprising a contactor for controlling the energization of a load circuit, a normally open start push button for momentarily energizing said contact'or for operation from an open to a closed circuit position, an undervoltage device operable with a time delay from a closed position to an open position, means responsive to the closing of said contactor for energizing said device to complete a holding circuit for said contactor, a

an operating coil and norclosed contacts being connected in series circuit relation with said holding circuit, a normally open stop push bottom for momentarily energizing said relay operating coil to open said holding circuit and deenergize said contactor and said undervoltage device, and connections completed, by the closing of said normally open relay contacts for maintaining said relay energized until saidundervoltage device operates to interrupt said holding circuit.

4. A time delay undervoltage protective system comprising a'contactorfor controlling the en-" ergization of a load circuit, a normally open start push button of the momentary contact type for energizing said contactor to operate it to a closed position, an undervoltage device operable with a time delay from a closed position to an open position, means responsive to the closing of said contactor for energizing said device to complete a holding circuit for said contactor, a relay procoil and normally open and closed contacts, said normally closed con-i tacts being connected in series circuit relation with said holding circuit, push button of the momentary contact type for energizing said relay operating coil to open said holding circuit, and connections completed by the closing of said normally open relay contacts for maintaining said relay coil energized until said undervoltage device operates to its open position.

5. A time delay undervoltage protective sys-' tem comprising a contactor operable between open and closed circuit positions for controlling the energization of a load circuit, a holding'cir-' cuit for said contactor for maintaining saidconr tactor in said closed circuit position, an undervoltage device responsive to the voltage of said" load circuit for maintaining said holding circuit closed so long as the voltage of said load circuit is above a predetermined value, said undervo1t-' age relay being operable with a time delay from a closed position to an open position when said, load circuit voltage decreases below said prede-- termined value, a relay provided with normally closed contacts connected in said holding circuit, circuit control means operable from an open position to a closed position to c'omplete momentarily an energizing circuit .for operating said re-1 lay to interrupt said holding circuit, and means operable with said relay for completing a maintaining circuit for said relay which circuit is controlled by said undervoltage device wherebysaid relay maintains said interruption of 'said holding circuit until said undervoltage device operates to open said holding circuit and said maintaining circuit.

' DUDLEY F. RICHARDSON,

a normally open stop" 

